Why Zebras Don't Get Ulcers. We feature an interview with biologist ROBERT SAPOLSKY about the effects of stress on humans and animals. Sapolsky is one of the first researchers to chart the effects of chronic stress, digestive problems and loss of libido, to name just a few. (Rebroadcast from 08/17/98)interview continuesinterview continues12:58:30 NEXT SHOW PROMO (:29) PROMO COPY On the next archive edition of Fresh Air. . . The bestseller "Blind Man's Bluff" about America's Submarine espionage during the cold war is now in paperback. We feature an interview with the authors: SHERRY SONTAG and CHRISTOPHER DREW. That's coming up on the next Fresh Air.